The invention relates to coating compositions based on mineral binders, polymers and fillers, to processes for producing coatings, and to water-redispersible dispersion powder compositions, processes for preparing them, and their use in the aforementioned coating compositions.
The use is known in the construction sector of coating compositions based on mineral binders, polymers and fillers for producing flexible coatings. Coating compositions of this kind are used, for example, as grouts, as described in U.S. Pat. No. 6,166,113 or DE-A 19620817. U.S. Pat. No. 4,710,526 discloses mortar compositions based on cement and cationic polymers for producing flexible coatings having good adhesive properties. KR 100913255 describes cementitious, polymer-modified mortar compositions for producing construction products having superior mechanical and chemical resistance. GB 1236263 discloses compositions based on mineral binders, fillers and polymers and also additives, such as hydroxy-carboxylic acids. U.S. Pat. No. 5,543,188 recommends membranes comprising a polymer layer that are impregnated with cementitious dry mixes. US 2008/0060299 and US 2006/0054059 describe flexible membranes based on mats made of plastic and equipped with flexible, cementitious, polymer-modified coatings. U.S. Pat. No. 5,484,478 recommends polycarboxylic acids comprising phosphpinic acid units as setting retarders for cementitious grouts, and the use thereof in petroleum extraction.
The existing coating compositions, however, result in coatings which over time slowly become brittle and hence are not permanently flexible. The embrittlement is manifested in a fall-off in the elongation at break or crack-bridging ability of the coatings. The crack-bridging properties of the coatings are essential, however, in order to protect the coated substrates. Cracks may be formed in the substrates, such as constructions, as a consequence of earthquakes, contraction processes, hygrothermal changes in length, or aging processes, or of other mechanical impositions. The flexible coatings are intended to bridge cracks of this kind and thereby to prevent water penetration into the substrates. If, however, the coatings have now become brittle and are therefore no longer flexible, the coatings themselves tend to crack over the course of time, or develop other kinds of damage, thereby allowing water to penetrate through the coatings into the underlying substrates, with the consequence of corresponding water damage. As a result of the embrittlement, then, the coatings no longer fulfill their purpose, or do so inadequately. Embrittlement occurs to an increased extent when the coatings are subject to damp or even to wet conditions. With permanently flexible coatings, i.e., coatings which have a durable flexibility, such damage ought to be prevented.
Against this background, the object was to provide coating compositions for producing permanently flexible coatings that are less susceptible to embrittlement, not least under damp or wet conditions, and, consequently, are durably flexible.